1. Field of the Invention
The present invention concerns an electromagnetic actuator of the type which generates a force resulting from substantially-constant current over the entire functional course of travel and which generates a reduced force in the absence of current, this actuator including a stator structure having two components, of which at least one incorporates three stator poles, and of a device which is movable in translational motion comprising two pairs of poles corresponding to two thin magnets magnetized in opposite directions; it further concerns the manufacture of pneumatic distributing devices utilizing these actuators.
2. Discussion of the Background
The general concept of such actuators, which can be produced incorporating plane or axial symmetry, are known in prior art.
In particular, the Applicant holds French Patent No. 89/08051, which discloses a single-phased electromagnetic actuator taking up little space. The actuators described in this patent are designed, in particular, for control of hard disk reading and writing heads or the actuation of plotting table pens. In these cases, a low electric time constant is sought.
For applications in which a strong force generated by electric power applied to the coil is sought, these three stator-pole actuators known according to prior art exhibit disadvantages. Indeed, when the width of the three poles match the course of travel of the rotor, the space available for housing the copper wire belonging to the electric trip coil may prove to be insufficient.
One may certainly increase the width of the poles beyond the dimension required for the expected course of travel of the rotor. In this case, it is also necessary to increase the width of the stator poles, a step which increases the cost price, since the high-quality magnetic materials used to produce the high-performance thin magnets are expensive.
Prior art further encompasses suggestions for producing multi-stage actuators having 2N+1 stator poles and 2N pairs of rotor poles, or 2N+1 pairs of rotor poles and 2N stator poles. However, in addition to the high cost of these actuators, these devices take up large amounts of space.